As is well known in the art, gear sets in gearboxes can deteriorate over time from a healthy, often new, condition to an unhealthy condition that may result in failure or, at least, inefficient operation of the gearbox. The challenge has been to develop a gearbox condition monitoring system that can provide early indications of impending problems. Prior efforts in this area have established that mesh frequencies and harmonics, by themselves, are usually poor indicators of gear condition. Additionally, variable speed machines, such as wind turbines, can have widely fluctuating loads and speeds, which further complicate gear mesh frequency analysis.
Prior attempts to monitor gears for ongoing deterioration have involved, for example, extracting and trending mesh frequency and harmonic amplitudes. It has been found, however, that this method does not work well as the method has relatively low sensitivity to developing faults. One prior effort along this lines is taught in U.S. Pat. No. 3,758,758 to Games et al., entitled “ROTATIONAL STATISTICAL VIBRATION ANALYSIS EMPLOYING SIDEBANDS AND/OR WEIGHTING.”
In view of these known concerns involved with prior efforts to monitor machine health, there remains a need to provide simple analysis methods that have improved sensitivity and lower influence from power and speed variability to accurately evaluate the health of machines, in particular, machines including gearbox systems.